feat: defer remote branch creation until first commit (#244)

* feat: defer remote branch creation until first commit

- For commit signing: branches are created remotely by github-file-ops-server on first commit
- For non-signing: branches are created locally with 'git checkout -b' and pushed when needed
- Consolidated duplicate branch creation logic in github-file-ops-server into a shared helper function
- Claude is unaware of these implementation details and simply sees it's on the correct branch
- No branch links are shown in initial comments since branches don't exist remotely yet

* fix: prevent broken branch links in final comment update

- Check if branch exists remotely before adding branch link
- Only add branch links for branches that actually exist on GitHub
- Add test coverage for non-existent remote branches
- Fixes issue where users would see broken branch links for local-only branches

* fix: don't show branch name in comment header when branch doesn't exist remotely

- Only pass branchName to updateCommentBody when branchLink exists
- Prevents showing branch names for branches that only exist locally
- Add test to verify branch name is not shown when branch doesn't exist

* tmp

src/entrypoints/prepare.ts

@@ -12,7 +12,6 @@ import { checkHumanActor } from "../github/validation/actor";
 import { checkWritePermissions } from "../github/validation/permissions";
 import { createInitialComment } from "../github/operations/comments/create-initial";
 import { setupBranch } from "../github/operations/branch";
-import { updateTrackingComment } from "../github/operations/comments/update-with-branch";
 import { configureGitAuth } from "../github/operations/git-config";
 import { prepareMcpConfig } from "../mcp/install-mcp-server";
 import { createPrompt } from "../create-prompt";
@@ -67,17 +66,7 @@ async function run() {
     // Step 8: Setup branch
     const branchInfo = await setupBranch(octokit, githubData, context);
 
-    // Step 9: Update initial comment with branch link (only for issues that created a new branch)
-    if (branchInfo.claudeBranch) {
-      await updateTrackingComment(
-        octokit,
-        context,
-        commentId,
-        branchInfo.claudeBranch,
-      );
-    }
-
-    // Step 10: Configure git authentication if not using commit signing
+    // Step 9: Configure git authentication if not using commit signing
     if (!context.inputs.useCommitSigning) {
       try {
         await configureGitAuth(githubToken, context, commentData.user);
@@ -87,7 +76,7 @@ async function run() {
       }
     }
 
-    // Step 11: Create prompt file
+    // Step 10: Create prompt file
     await createPrompt(
       commentId,
       branchInfo.baseBranch,
@@ -96,7 +85,7 @@ async function run() {
       context,
     );
 
-    // Step 12: Get MCP configuration
+    // Step 11: Get MCP configuration
     const additionalMcpConfig = process.env.MCP_CONFIG || "";
     const mcpConfig = await prepareMcpConfig({
       githubToken,